3 Answers
3

The fashion for the last several decades is to use less and lighter punctuation. As there is no danger of misunderstanding the elements of the sentence without the comma, leaving it out is preferred. If one were to read the short sentence aloud there would be no need for even a short pause.

To be fair, this depends entirely on the style book. Some, like The Economist prefer short, initial appositives to be left without an ending punctuation; other, more verbose stylebooks request its presence.
– HalosGhostOct 22 '14 at 4:45